Welcome to tex.sx! It's not necessary to sign your questions (as there is already a box with your username below it) or to begin them with a greeting.
–
lockstepApr 16 '11 at 11:44

Since you have some responses below that seem to answer your question, please consider marking one of them as ‘Accepted’ by clicking on the tickmark below their vote count. This shows which answer helped you most, and it assigns reputation points to the author of the answer (and to you!).
–
doncherryAug 17 '11 at 21:29

4 Answers
4

Use the scrextend package (which is part of KOMA-script) and its \deffootnote macro. See section 3.14 of the KOMA-script manual for details. (You may also use one of the KOMA-script classes instead of scrextend.)

\documentclass[12pt]{article}
\usepackage[paperheight=8cm]{geometry}
% just to reduce sample size
\usepackage{hanging}
% provides the \hangpara command
\usepackage[flushmargin]{footmisc}
% sets the footnote mark just left of the left margin border
\renewcommand{\footnotemargin}{1em}
% changes the above and sets the footnote mark just right of the left margin border.
\newcommand{\fn}[1]{\footnote{\hangpara{3em}{1} #1}}
% makes a new footnote command \fn{} with a hanging indent of 3em (hanging indent starts after the first line)
\begin{document}
Hello\fn{This is the first line of the very, very, very, very, very, very, very, very, very, very long footnote
and this is the second line of the very, very, very, very, very, very, very, very long footnote
and this is the third line of the very long footnote.}
World\fn{This is the first line of the very, very, very, very, very, very, very, very, very, very long footnote
and this is the second line of the very, very, very, very, very, very, very, very long footnote
and this is the third line of the very long footnote.}.
\end{document}

Regarding the \footnotemargin: This setting works for one- and two-digit footnote marks. If you only have one-digit marks, {0.5em} might be better; if you have three-digit footnote marks, you might want to change this value to {1.5em}, otherwise the first digit will stick into the left margin.